Lennox G50UH(X) SERIES Guide

05/00
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504,121M
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G50UH(X)
SERIES
Litho U.S.A.
504,121M
5/2000
WHAT TO DO IF YOU SMELL GAS:
Iftheinformationinthismanualisnotfollowed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of
life.
WARNING
-
Do not try to light any appliance.
-
Do not touch any electrical switch; do not use any
phone in your building.
-
Immediatelycallyourgassupplierfromaneighbor’s
phone. Follow the gas supplier’s instructions.
-
Ifyou cannotreachyourgassupplier,callthefire de-
partment.
-
Extinguish any open flames.
GAS FURNACE
Do not store or use gasoline or other flam-
mable vapors and liquids in the vicinity of
this or any other appliance.
Installation and service must be performed by
a qualified installer, service agency or the gas
supplier.
. 2000 Lennox Industries Inc.
Dallas, Texas, USA
£

Page 2
G50UH(X) Parts Identification
DURALOKTM HEAT
EXCHANGER
ASSEMBLY
UPPER ACCESS
PANEL
BURNERS
BLOWER
MOTOR
GAS
MANIFOLD
CABINET
CONTROL BOX
GAS
VALVE
COMBUSTION AIR
PROVING
(PRESSURE) SWITCH
COMBUSTION AIR
INDUCER
BLOWER ACCESS
PANEL
FLUE
COLLAR
TOP CAP
SURELIGHT
Z
Z
CONTROL BOARD
NAMEPLATE
FIGURE 1
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool. Breathing this may cause lung
cancer.(Fiberglasswool is knowntotheStateofCal-
ifornia to cause cancer.)
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
availablefromaddressshownbelow,orcontactyour
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379-9900
NOTE - This manual must be left with the equipment
user.
WARNING
Do not set thermostat below 60°F (16°C) in heating
mode. Setting thermostat below 60°F (16°C) reduces
the number of heating cycles. Damage to the unit
may occur that is not covered by the warranty.
WARNING
Ifoverheatingoccursorifgassupplyfailstoshutoff,
shutoffthemanualgasvalvetothe appliancebefore
shutting off electrical supply.
CAUTION
Before attempting to perform any service or mainte-
nance, turn the electrical power to unit OFF at the
disconnect switch.

Page 3
WARNING
Do not use this furnace if any part has been under
water. Immediatelycallaqualifiedservicetechnician
to inspect the furnace and to replace any part of the
control system and any gas control which has been
under water.
IMPORTANT
Any additions, changes, or conversions required in
order for the appliance to satisfactorily meet the ap-
plication needs must be made by a Lennox service
technician using factory specified and approved
parts.
WARNING
Improperinstallation,adjustment,alteration,service
ormaintenancecancausepropertydamage,person-
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
Important Directions
1 - Keep the furnace area clear and free of combustible
material, gasoline, and other flammable vapors and
liquids.Ifitisinstalledinaninsulatedarea,thefurnace
mustbekeptfreeofinsulatingmaterial.Insulatingma-
terial may be combustible.
2- DO NOT obstruct air flow to unit. Unit must receive an
unobstructed flow of combustion and ventilating air.
3- DO NOT store chlorine or fluorine products near unit
or introduce these products into the combustion air.
These products can cause furnace corrosion.
4- DONOTdrawreturnairfromaroomwherethisfur-
nace, or any other gas appliance (ie., a water heat-
er),isinstalled.Whenreturnairisdrawnfromaroom,
anegativepressureiscreatedintheroom.If agasap-
pliance is operating in a room with negative pressure,
the flue products can be pulled back down the vent
pipe and into the room. This reverse flow of the flue
gas may result in incomplete combustion and the
formation of carbon monoxide gas. This toxic gas
might then be distributed throughout the house by the
furnace duct system.
WARNING
The blower door must be securely in place when the
blower and burners are operating. Gas fumes,which
could contain carbon monoxide, can be drawn into
the living space resulting inpersonalinjury or death.
Your furnace is a gas appliance. It is critical that the gas
supplied to the unit be completely burned to avoid the pro-
duction of carbon monoxide gas. Complete combustion of
the gas requires, but is not limited to, correct gas pressure
and gas flow rate, adequate combustion air and proper
venting.
WARNING
Carbon monoxide gas is invisible, odorless, and
toxic.
Exposure to carbon monoxide gas can cause personal inju-
ry and even death to all occupants, including pets. Any item
that is powered by, or gives off heat from, a combustion pro-
cess (including lawn mowers, automobiles, and fireplaces)
hasthepotentialtoproducecarbonmonoxidegas.Because
ofthis,Lennoxrecommendstheuseofa carbonmonox-
ide detector in your home, even if you do not own gas
appliances. Reliable detectors are available at reasonable
retail prices. Contact your Lennox dealer for more details
about this investment in your safety.
Yourfurnaceis designedtomeetstandards setbynation-
al agencies. It should operate safely when properly
installed and maintained. However, the unit’s perfor-
mance can be greatly impacted by the individual installa-
tion and the operating environment. It is your responsibil-
ity to ensure that this appliance is maintained. Proper
maintenanceis criticalforyoursafety andthesatisfactory
operationoftheproduct.Lennoxstronglyrecommends
annualinspectionandmaintenanceofthisappliance.
Contact your Lennox dealer for an inspection by a quali-
fied service technician.
Lighting Information & Operation
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
BEFORE LIGHTING smell all around the appliance area
forgas.Besuretosmellnexttothefloorbecausesomegas
is heavier than air and will settle on the floor.

Page 4
The gas valve on the G50UH(X) is equipped with either a
gas control knob or lever. Use only your hand to turn the
gas control knob or push the gas lever. Never use tools. If
theknoborleverwillnotmovebyhand,donottrytorepair
it. Call a qualified service technician. Force or attempted
repair may result in a fire or explosion.
Placing the G50UH(X) furnace into operation:
G50UH(X) units are equipped with a SureLight
Z
ignition
system. Do not attempt to manually light burners on these
furnaces. Eachtimethethermostatcallsfor heat, the burn-
ers will automatically light. The ignitor does not get hot
when there is no call for heat on units with the SureLight
Z
ignition system.
Operating the Gas Valve (Figures 3, 4and 5)
1- STOP! Read the safety information atthe beginning of
this section.
2 - Set the thermostat to the lowest setting. See figure 2.
3 - Turn off all electrical power to the unit.
THERMOSTATS
FIGURE 2
4 - This furnace is equipped with an ignition device which
automatically lights the burners. Do not try to light the
burners by hand.
5 - Remove the upper access panel.
6-
White Rodgers 36E/36F Gas Valve - Switch gas
valvelevertoOFF.Seefigure3fortheWhiteRodg-
ers 36E valve and figure 4 for the White Rodgers
36F valve.
Honeywell VR8205 Gas Valve - Turn knob on gas
valveclockwise toOFF.Donotforce.Seefigure
5.
7 - Wait fiveminutestoclearoutanygas.Ifyou thensmell
gas, STOP! Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s instruc-
tions. If you do not smell gas go to next step.
8-
WhiteRodgers 36E/36FGasValve- Switchgasvalvele-
ver to ON. See figure 3 for the White Rodgers 36E
valveandfigure4fortheWhiteRodgers36Fvalve.
Honeywell VR8205 Gas Valve - Turn knob on gas valve
counterclockwise to ON. Do not force.
White Rodgers 36E Series Gas Valve
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
FIGURE 3
White Rodgers 36F Series Gas Valve
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
FIGURE 4
ON
OFF
Honeywell VR8205 Series Gas Valve
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
FIGURE 5
9 - Replace the upper access panel.
10 - Turn on all electrical power to to the unit.
11 - Set the thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12 - If the appliance will not operate, follow the instructions
“TurningOffGastotheUnit”andcallyourservicetech-
nician or gas supplier.
Turning Off Gas to the Unit
1 - Set the thermostat to the lowest setting.
2 - Turnoff all electrical powerto theunit if service is to be
performed.
3 - Remove the upper access panel.

Page 5
4-
White Rodgers 36E/36F Gas Valve - Switch gas
valve lever to OFF.
Honeywell VR8205 Gas Valve - Turn knob on gas
valve clockwise to OFF.Donotforce.
5 - Replace the upper access panel.
Filters
This unit is not equipped with a filter or rack. A field-pro-
vided, high-velocity filter is required to ensure proper unit
operation.
A filter must be in place any time the unit is operating.
Seasonal Inspections
A qualified service technician should inspect the complete
system each season (heating and cooling). The following
maintenance procedures should only be conducted by a
qualified service technician. Do not attempt to service
the unit in any way.
Venting System
WARNING
Asphyxiation Hazard
The exhaust vent for this furnace must be securely
connected to the furnace flue collar at all times.
For your safety and to fulfill the terms of the limited
warranty,aqualifiedservicetechnicianmustannual-
ly inspect this furnace and its vent system.
Annually (before heating season) inspect furnace venting
system, vent cap, heat exchanger and burners for corro-
sion, deterioration, or deposits of debris. Remove any ob-
structions.
Inspect thefurnace venting system to make sure it is in
place, physically sound and without holes, corrosion, or
blockage. The vent connector must be correctly posi-
tioned and sloped upward. The vent connector must be
physically sound, without holes or excessive corrosion.
Inspect the furnace return air duct connection. The duct
mustbesealedtothefurnaceanditmustterminateoutside
the space containing the furnace.
Inspect the physical support of the furnace to guarantee
that it is sound. The support must not sag and must not
have cracks or gapsaround thebase ofthefurnace. There
must be a seal between the furnace base and the support.
During a seasonal check, the service technician will in-
spect the indoor blower and the burner flames along with
the venting system.
Blower
Check blower wheel for any debris and clean it, if neces-
sary.Theblowermotorispre-lubricatedforextendedbear-
ing life. No further lubrication is needed.
Burner Flame
CAUTION
To ensure proper operation, a qualified technician
should annually check the burner flame.
Service Reminder
Callyour Lennoxservice technicianif the unitwillnotoper-
ate. Before calling, always check the following to be sure
service is required.
1 - Check that electrical disconnect switches are ON.
2 - Check room thermostat for proper setting.
3 - Replace any blown fuses or reset circuit breakers.
4 - Gas valve should be ON.
5 - Air filter should not be plugged, which wil limit air flow.
6 - Is gas turned on at meter?
7 - Is manual main shut-off valve open?
Record the modelandserialnumber ofthefurnace.These
numbers areon the unitnameplate, whichis located below
the burners.
Serial Number ________________________________
Model Number ________________________________
Safety Precautions
If you discover any of the following, shut down your
unitandcontactaLennoxdealerforan inspectionbya
qualified technician.
-
If you repeatedly hear any new or unfamiliar sounds
whileyourunitisoperating,theremaybeaproblem.For
example, poorly performing burners can produce unfa-
miliar noises.
-
Ifyousmellanyunusualodors,yourunitmay beoperat-
ing improperly. For example, units can give off unfamil-
iar odors if components are required to operate in ab-
normal conditions.
-
Lookforvisiblesignsofamalfunctioningunit.Examples
includeunusualamountsofcondensateonwindows in-
side your house, visibly burnt components or unusual
dirt or rust accumulations on the vent pipe or in the unit.
-
If you experience headache, nausea, fatigue, or dizzi-
ness, thecause couldbeexposure to carbonmonoxide
gas. This is often misdiagnosed as the flu because
symptoms are similar. If you suffer from flu-like symp-
toms that are exaggerated at home, but seem to sub-
side while you are away from the house, exposure to
carbon monoxide could be the cause.
Your vigilance may pay off in early detection of a problem
before either personal injury or property damage occurs.
Do not hesitate to contact a qualified service technician as
an investment in your well being.

Page 6
Planned Service
Youshould expectaservicetechniciantocheck the follow-
ing items during an annual inspection. Power to the unit
must be shut off for the service technician’s safety.
Fresh air grilles and louvers (on the unit and in the room
where the furnace is installed) - Must be open and unob-
structed to provide combustion air.
Burners - Must be inspected for rust, dirt, or signs of water.
Vent pipe -Mustbeinspectedforsigns of water, damaged
or sagging pipe, or disconnected joints.
Unit appearance - Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
Blower access door - Must be properly in place and pro-
vide a seal between the return air and the room where the
furnace is installed.
Return air duct - Must be properly attached and provide
an air seal to the unit.
Operating performance - Unit must be observed during
operationtomonitorproperperformanceoftheunitandthe
vent system.
Combustion gases -Flueproducts mustbe analyzedand
compared to the unit specifications.
Problems detected during the inspection may make it nec-
essary to temporarily shut down the furnace untilthe items
can be repaired or replaced.
Pay attention to your furnace. Situations can arise be-
tweenannualfurnaceinspectionsthatmayresultinunsafe
operation.Forinstance,itemsinnocently storednexttothe
furnacemayobstructthe combustionairsupply.Thiscould
cause incomplete combustion and the production of car-
bon monoxide gas.